Optical fingerprint sensors have been widely used due to such an advantage as long-distance sensing. In addition, in order to reduce the noise contained in a fingerprint detection result, typically fingerprint detection is performed by the optical fingerprint sensor through an active detection circuit for detecting a voltage.
Typically, the active fingerprint detection circuit in the related art includes a first switching transistor, a photodiode connected in series with the first switching transistor, a voltage following transistor, and a second switching transistor connected in series with the voltage following transistor. During operation, the first switching transistor is turned on, so as to reset a gate voltage of the voltage following transistor. The gate voltage, which varies due to irradiation of the photodiode, is then outputted to a columnwise output bus via a source electrode of the voltage following transistor and the second switching transistor in an on state, so as to acquire fingerprint data.
However, for a glass-based amorphous silicon process or a low-temperature poly-silicon process, the voltage following transistor in the active fingerprint detection circuit is a thin film transistor (TFT). Due to the characteristics of the TFT itself, a threshold voltage drift may occur for the TFT with the elapse of time, so a following effect of the voltage following transistor is non-ideal. Hence, a drift may occur for output data of the active fingerprint detection circuit, and it may be impossible for the active fingerprint detection circuit to detect a fingerprint normally.